Method and apparatus for the extrusion of metal



April 18, 1933. w. TRAVIS METHOD AND APPARATUS FOR THE EXTRUSION OF METAL 2 Sheets-Shegt 1 Filed Nov. 4. 1931 S 12 l 20 19 7'/ Y //1s 18 S s. .I

6 5mm Pm@ MM- E j )2M ,4FM/vifs' I April 18, 1933. w. TRAVIS 1,904,907

METHOD AND APPARATUS FOR THE EXTRUSION 0F METAL Filed Nov. 4. 1931 2 Sheets-Sheet 2 Fig. 2.

Patented 18, 1533 mauri-:li v'srtmas PATENT orsi-ca e i i I j ornucxnar, ma@

Application llod Immbex 4, 1981, Serial lo. 578,987, and in Great Britain :Novemberi 5, 1930.

This invention relates to extrusionprocceses which take place under conditions which involve a definite fall of temperature so that thematerial, which is supplied tothe apparatus in the molten state, 1s extruded in the plastic state. kThe invention accordingly ap- -plies to a large number of materials, both metallic and otherwise.

The ap aratus used includes an extrusion l0 chamber om which the plastic material is driven forward through a die or dies which impart to it the appro riate shape and dimensions as it leaves t e chamber. In addition it also includes two other parts struc- 16 turally distinct from the extrusion chamber, namely, means such as a pump .device for giving impulsive movement to the molten material and aj connecting passage or passages between this device and the extrusion 20 chamber. Generally the device will consist of several units each with its connecting passage leading .tothe extrusion chamber. The passage or each passage, where there are several, is materially, smaller in cross-section than the chamber so that a definite temperature control of the condition of the material throughout the cross-section of therpassage or eachv passage ma be exerted. is difference in cross-sect1on constitutes the structural distinction between the passage or passa es and the-extrusion chamber.

n accordance with the invention the molten material is fed forward towards the .extrusion chamber in a yseries of impulses and the material is subjected to cooling before it enters the extrusion chamber so that the material in that chamber is in a lastic state; these impulses, being transmitted) to the plastic material in the chamber, force it forward 40 through the die or dies.v As a result 4of the cooling action on the incoming material there is a greater uniformity in t e condition of the material in the extrusion chamber and in I particular it ismadeimpossible for a thread of molten material to pierce through the main body of plastic materlal and reach a die.

The apparatus comprises a device such asy l made such that the impu nating with periods of rest.4 This works in conjunction with a cooling ypassage through.' which the materialY passes prior to enterin the extrusion chamber, this being arranged to remove suilicient heat to convert the mate- `rial from the molten to the plastic state. We

prefer to use a vnumber of pumps feeding a single extrusion chamber, the arrangement f being suchfthat the iow impulses are deliveredr'in successionf at different points round C3 the `circumference of the extruslon chamber.

The pumps may be arranged in a convenient position for operation and connected to the points of delivery by pipes which are controlled in temperature so as to maintain th material in the molten state whilst assing through them. This may be carrie out by passing electric currents through the pipes, for instance, low voltage currents flowmg along the pipes and heating them and their contents by the resistance method. The

4cooling passage will then be arranged nspaced round the chamber and numbered 1n order from one to six, the sequences of the impulses may be arranged 'in the following order, 1, 4, 2, 5, 3, 6. y

The invention will be described further with the aid of the accompanying diagrammaticpdrawings which indicate hovv` the apparatus can be constructed and arranged for the extrusion of lead to form a pipe or a sheath of anelectric cable.

y I n these drawings, Figure 1 is an end elevation, with parts in section, of the apparatus; 1 v Figure 2 is a side elevation of the die box; and

Figure 3' is `a longitudinal central section of the d ie box.`

`The die box 7 has a central aperture 8 100 alsl c -fhiugh w'hi h" the cable, when the v@pimms is wif Acable.. AThe annular s ace 9'within the die forapplying a sheathto a box is full of plastic ead and may be pro- -vided with means for -maintainingit at an appropriate, temA erature to ensure thatthe has across-head 16 4working in a propriete.l

guides. In the upper end of Leac pump 11 is an inlet passageadcontrolledby a valve 18 which opens during the downward stroke of the ram, so las toadmitlead vto the cylinder. 'The side ALpassage '19y -lead's'ftothe de- I fthe upwardstroke commences.

livery valve 20 which is closed. .during .the

downward stroke .of the ram, but o ns when he inlet valve 18 closes atthis point so that theupward stroke forces the molten metal to flow along the pipe 10 into the appropriate cool-' in'passage and from there-into the die box.

he rotation ofthe cranks 15 causes this impulsive supply of molten metal to be `sent out by each -pump in succession.

In the arrangement shown'lthere are two crank shafts which are arranged side by side andconnected. together 'so as torotate chronously.4 The arrangement of the cranks .miis such thatthe impulses reachthe cooling passages in the order .1, 4, 2, 5, 3, 'previously mentioned. In the position shown inFigure in lead past its valve 118. teapum -vat the left-handside has justcomple' its elivery,-

1 the right-hand pumpA has com leted its de livery to cooling chamber l-an is drawing.'

manner convement to 'chamber'` 4.

'-It .be understood that there twofj other pumpson the left-hand side connected to 5 Aand 6 and two otherson-the; rig t-hand'side connectcdto chambers 3, and' 2. .These drawings, ut

eirnpresence is indicatedby the three-throw cra:

shaft at each side.y

'Each of the cooling passages is made as-a ring to a neck at therrear4 short cylinder ta or inlet end, an a cooling arrangement is v'provided by ducts 21 formed inthe wall of the cylinder'through whichliquid (for finstance oil) can be assed, entering by the pipe22 and leaving y the pipe 23. As this wall has considerable thickness to withstand the under which it works, it is preferab e to arran the coo duct nearthe inner surface o this wall.l can be done by boring out the cylinder 24 to a greater for extrusion does not be.

metal ap lied to the rear of cal cham c r will force forward :the plastic 'etal therein and cause -it to issueinthe formum s cannot'beshown "in the diameter than that of its working space fand inserting a liner 25 to make up the diierence, thisliner ha outer face. T is p oovev in combination with the inner sur ace of the cylinder --24 a helical groove cnt .in its makes a closed helical passadge for whichinlet and outlet ports are provi ere eatin o e i isn fit can be carrie out aspixlcated di tri'c energy forheatingis made ed in the wallof -niatical-lyin Figurel., The sulpply, of letcj wayo -t e transformer 36, thelow voltage side of which is connected by conductors34 and 35 to the `diejbox'jfl .and thepot :12. It will under-'-v y stood-that the conductors 34 .and `35 are of heavysectionand thattheprinci al'resstance inthe retnrncircuit/is rovi ed-.by the pipes 10, soV that-heating wi l be'QW-in' these pipes. 1n order to 'produceapproximateuniformity of-heatingin ftheseveral pipes it will., of course, beneces'sary tojensure" that their resistancesl `are approximately 'i ual. Owing to -the diagrammaticfnature o Figure 1 it does not show this equaliza-n tion.

As shown in Fi' gare a the' die box 'zaclihinsf outer and inner dies and 31 located in the centre of the annular space 9 ,which'is ener-J ally of conical form, the side walls. gra uallfyfconverging as the dies are approached. The A of this chamber. Thebod` of the diebox 'near its ends to revent the tron of.

e'cblepesinsthmug'hthe y ofpngue r eannular c oni'- excessiveheatto die-box. v

"It 4winne' seen ths'fhe Kof a tube between the ,dies 3l-:and 430.

The dies will,l in be 'mounted may be replaced Vby others cffsutable -size from the ap aratus'vary.

Whatlc cimas m tosecureb Letters ateiitis:-

. f1. Afme dof extrusioncomprisingfeeding j molten material towardsA an extrusion', chamber by a series of 'and 'in a stream of :much smaller cross-section than .cooling passages are connectedwith tlevrear or removalso that they ias thepfdmensions of the. pr oduct required ventlion and desire the'cross-'section of the extrusion chamber, a

subjectingthisstream to coolin before itI enters the extrusion chamber so t at the ma'- terial therein 1s in a lastic state, and forcing the plastic material y the feeding impulses through the extrusion chamber and througha die mounted therein.

trusion chamber withqa die" which 12. Extrusion apparatus Ian' ex' oug material is forced out impulses actingon molten material, a p conducting the material from the impulse means for producing,

producing means into the said chamber, said passage being of much smaller cross-section than the extrusion chamber, and cooling means act' on the material in the said passage so that 1t enters the chamber in a plastic state.

3. Extrusion appraratus comprising an extrusion chamber, om which plastlc material is forced through a die, means for feeding this chamber with plastic material at a number of points round its circumference, said means comprising impulse producing devices applying their, impulses in succession to molten material, means for conducting the molten material from each of said devices to the feeding oints of the said chamber, each of said con ucting means comprising a passage of much smaller cross-section than the extrusion chamber, and a cooling device acting on each of said passages and serving to convert the material to the lastic state before it enters the extrusion c amber.

4. Extrusion a paratus com rising an extrusion chamber gom which pPastic material is forced out through a die, a pump, a heated pipe from the pump to the chamber and a coolin passage of much smaller cross-section than t e extrusion chamber, said passa being attached to the ipe and connectlng it with the chamber so t at the molten material acted on by the pum is maintained molten while passlng throng the pipe and is then cooled to'the lastic state before it enters the extrusion c amber.

In testimony whereof I aix my signature.

WILLIAM TRAVIS. 

